Riding lawn mower

ABSTRACT

Riding lawn mower switchable between mulching and bagging modes includes: a delivery passage for delivering grass, cut by cutting blades in a housing, from the housing to a receptacle by delivering air; and a scroll guide provided in an entrance of the passage for directing the grass clippings to the passage. An overall shape of the scroll guide as viewed in top plan is a substantial isosceles triangle extending into the housing while tapering forward from a scroll guide&#39;s base section located in the entrance and as viewed in side elevation is a substantial triangle tapering forward from the base section. Left and right side surfaces of the scroll guide each comprises lower and upper slanting surfaces formed as different slants, each of which gradually increases in area from the distal end of the scroll guide toward the base section.

FIELD OF THE INVENTION

The present invention relates to riding lawn mowers switchable between abagging mode and a mulching mode.

BACKGROUND OF THE INVENTION

Among the conventionally-known riding lawn mowers is the so-calledrotary lawn mower which cuts grass by rotating a cutting blade,accommodated in a downwardly-opening housing, along the surface ofgrass. Examples of such a rotary lawn mower include a type for use in amulching mode and a type for use in a bagging mode. The lawn mower foruse in the bagging mode collects grass cut by the cutting blade (i.e.,cut grass or grass clippings) in a grass clippings receptacle, while thelawn mower for use in the mulching mode chops the grass clippings intofiner pieces within the housing and discharges the thus-chopped glassclippings downward of the housing.

An example of the riding lawn mower for use in the bagging mode is knownfrom Japanese Examined Patent Application Publication No. HEI-5-55086(hereinafter referred as “Patent Literature 1”) and Japanese PatentApplication Laid-open Publication No. 2009-50222 (hereinafter referredas “Patent Literature 2”). More specifically, the riding lawn mowerdisclosed in Patent Literature 1 and Patent Literature 2 includes aguide section provided on a front portion of the inner surface of thehousing and centrally in the width direction of the housing. The guidesection is formed in a generally V shape tapering from the front innersurface portion of the housing toward an entrance of a cut grass (glassclippings) delivery passage as viewed in top plan.

An example of the riding lawn mower for use in the mulching mode isknown from Japanese Patent Application Laid-open Publication No.HEI-9-187139 (hereinafter referred as “Patent Literature 3”). Morespecifically, the riding lawn mower disclosed in Patent Literature 3 hasan opening formed in a rear portion of the housing, and the opening isclosed with a detachable wall member. With the wall member closing theopening, the riding lawn mower can be used in the mulching mode. Withthe wall member detached to open the opening, the riding lawn mower canbe used in a so-called rear discharge mode where grass clippings aredischarged rearward through the opening. Namely, for switching betweenthe mulching mode and the rear discharge mode, it is necessary to attachor detach the wall member that is one type of mode-specific componentpart. Further, the riding lawn mower disclosed in Patent Literature 3includes a guide section provided on a front portion of the innersurface of the housing and centrally in the width direction of thehousing. The guide section is formed in a generally V shape taperingfrom the front inner surface portion of the housing toward the rearopening of the housing as viewed in top plan.

However, it is often inconvenient to use such two types of lawn mowersdepending on intended purposes. So, recent years have seen developmentof a technique for allowing a single riding lawn mower to be used, oroperable, both in the bagging mode and in the mulching mode. To thatend, it is required that the single riding lawn mower be able toefficiently discharge grass clippings downward of the housing in themulching mode and efficiently collect grass clippings in a grassclippings (cut grass) receptacle. Besides, when the riding lawn mower isswitched from the bagging mode to the mulching mode or from the mulchingmode to the bagging mode, there is a need to replace a predeterminedcomponent part of the previous or switched-from mode with a componentpart dedicated or specific to the new or switched-to mode, and suchcomponent part replacement is a troublesome operation.

SUMMARY OF THE INVENTION

In view of the foregoing prior art problems, it is an object of thepresent invention to provide an improved technique which can optimizeflows of grass clippings delivering air and grass clippings irrespectiveof whether the riding lawn mower is in the mulching mode or in thebagging mode.

In order to accomplish the abovementioned object, the present inventionprovides an improved riding lawn mower, which comprises: a housingopening downward; a cut grass receptacle disposed rearward of thehousing; left and right cutting blades accommodated in the housing androtatable in generally the same plane in such a manner as to not onlycut grass but also generate cut grass (grass clippings) delivering air;a cut grass delivery passage (grass clippings delivery passage) fordelivering grass, cut by the left and right cutting blades, from awidthwise center portion of the housing to the cut grass receptacle byuse of the cut grass delivering air; a mechanism for switching the lawnmower between a bagging mode in which grass cut by the cutting blades isdelivered from the housing to the cut grass receptacle and a mulchingmode in which grass cut by the cutting blades is discharged downward ofthe housing; and a scroll guide provided in an entrance of the cut grassdelivery passage for directing the cut grass and the delivering air tothe cut grass delivery passage while swirling the cut grass and thedelivering air within the housing. An overall shape of the scroll guideis, as viewed in top plan, a substantial isosceles triangle extendinginto the housing while tapering forward from a base section of thescroll guide located in the entrance, and, as viewed in side elevation,a substantial triangle tapering forward from the base section, left andright side surfaces of the scroll guide each comprising a lower slantingsurface and an upper slanting surface formed as different slants belowand above a substantial middle height portion thereof, each of the lowerslanting surface and the upper slanting surface being shaped togradually increase in area in a direction from the distal end of thescroll guide toward the base section.

In the lawn mower of the present invention, which is switchable betweenthe bagging mode and the mulching mode, the scroll guide is provided inthe entrance of the cut grass delivery passage. The scroll guide is amember for directing the cut grass and the delivering air to the cutgrass delivery passage while swirling the cut grass (grass clippings)and delivering air within the housing. The scroll guide as viewed in topplan has an overall shape that is a substantial isosceles triangleextending into the housing while tapering forward from the base sectionof the scroll guide located in the entrance, and the scroll guide asviewed in side elevation has an overall shape that is a substantialtriangle tapering forward from the base section. The left and right sidesurfaces of the scroll guide each comprise the lower slanting surfaceand the upper slanting surface that are formed as different slants, andthus, by setting appropriate slant angles of the aforementionedindividual slanting surfaces, it is possible to optimize flows of thegrass clippings delivering air and grass clippings irrespective ofwhether the lawn mower is in the mulching mode or in the bagging mode.Thus, the grass clippings can be efficiently discharged downward of thehousing in mulching mode, while the grass clippings can be efficientlycollected in the grass clippings receptacle in the bagging mode.Besides, when the lawn mower is switched from the bagging mode to themulching mode or from the mulching mode to the bagging mode, there is noneed to replace a predetermined component part specific to the previousor switched-from mode with a component part specific to the new orswitched-to mode in order to optimize the flows of flows of the grassclippings delivering air and grass clippings.

In the mulching mode, the present invention can prevent grass clippings,swirling within the housing, from undesirably falling down in theneighborhood of the entrance of the grass clippings delivery passage(cut grass delivery passage) and thus can effectively retain the grasswithin the housing (i.e., achieve an enhanced grass retainingcharacteristic or performance). Therefore, the present invention candischarge the grass clippings downward of the housing after sufficientlychopping the grass clippings to finer pieces. Further, in the baggingmode, the present invention can efficiently deliver grass clippings,swirling within the housing, to the grass clippings delivery passage

Preferably, the lower slanting surfaces of the left and right sidesurfaces of the scroll guide extend generally normally to the lowersurface of the housing. Thus, in the mulching mode, the grass clippingsswirling within the housing can be caused to smoothly swirl by means ofthe left and right side surfaces of the scroll guide as well. Further,the upper slanting surfaces of the left and right side surfaces of thescroll guide slant upward from the distal end of the scroll guide towardthe base section. Namely, the left and right upper slanting surfaces aretwisted surfaces relative to the upper ends of the left and right lowerslanting surfaces, so that a great quantity of grass clippings swirlingwithin the housing can be delivered with an enhanced efficiency. In thisway, the present invention can achieve not only enhancement of a grassdelivery efficiency with which to discharge grass clippings in thebagging mode but also enhancement of the so-called grass retainingcharacteristic.

Preferably, the distal end of each of the left and right cutting bladesis located at a higher position than the distal end of the scroll guide.Thus, the grass clippings swirling within the housing is insusceptibleto swirling resistance from the distal end of the scroll guide, as aresult of which the present invention can even further enhance the grassretaining characteristic.

Preferably, of the base section of the scroll guide, surfaces facingradially inward of the housing are shaped to extend along the innerperipheral surface of the housing. Thus, the present invention can evenmore smoothly swirl the grass clippings within the housing.

Preferably, at least a rear half portion of the lower surface, locatedwithin the housing, of the scroll guide slants toward the base sectionlocated in the entrance of the cut grass delivery passage. Thus, grassclippings swirling within the housing can even more smoothly swirlwithout meeting swirling resistance from the lower surface of the scrollguide

The following will describe embodiments of the present invention, but itshould be appreciated that the present invention is not limited to thedescribed embodiments and various modifications of the invention arepossible without departing from the basic principles. The scope of thepresent invention is therefore to be determined solely by the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain preferred embodiments of the present invention will hereinafterbe described in detail, by way of example only, with reference to theaccompanying drawings, in which:

FIG. 1 is a left side view of an embodiment of a lawn mower of thepresent invention;

FIG. 2 is a left side view of a housing, grass clippings deliverypassage, chute and grass clippings receptacle shown in FIG. 1;

FIG. 3 is a left front upper perspective view of the housing shown inFIG. 1;

FIG. 4 is a sectional view of the housing, grass clippings deliverypassage and chute taken along a widthwise centerline of the lawn mower;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a bottom view of the housing, left and right cutting bladesand sections around the left and right cutting blades shown in FIG. 5;

FIG. 7 is an enlarged view of a scroll guide and shutter mechanism shownin FIG. 4;

FIG. 8 is an exploded view of the grass clippings delivery passage,scroll guide and shutter mechanism shown in FIG. 4;

FIG. 9 is a view taken in a direction of arrow 9 of FIG. 7;

FIG. 10 is a perspective view of the scroll guide shown in FIG. 7;

FIG. 11 is a view explanatory of relationship between the cutting bladesand the scroll guide shown in FIG. 4;

FIG. 12 is a perspective view of the shutter mechanism shown in FIG. 3;

FIG. 13 is an exploded view of the shutter mechanism shown in FIG. 12;

FIG. 14 is a perspective view of an operation section shown in FIG. 1;

FIG. 15 is an exploded view of the operation section shown in FIG. 14;

FIG. 16 illustrates behavior of the scroll guide and shutter mechanismshown FIG. 4 when the lawn mower is in a bagging mode; and

FIG. 17 illustrates behavior of the scroll guide and shutter mechanismshown FIG. 4 when the lawn mower is in a mulching mode.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, the terms “front”, “rear”, “left”,“right”, “upward”, “downward” etc. are used to refer to directions asviewed from a human operator of a riding lawn mower of the presentinvention.

Now, a description will be given about an embodiment of the riding lawnmower 10 of the present invention. As shown in FIGS. 1 and 2, the ridinglawn mower 10 is a working machine of a type in which the human operatorrides on a seat 11 and drives a grass cutting system while running thelawn mower 10 by means of a single power source 12.

The power source 12 is, for example, in the form of an electric motorand provided on a front upper section of a machine frame 13 (vehiclebody frame 13) of the lawn mower 10. The machine frame 13 has left andright front wheels 14 provided on left and right sides of a frontsection thereof and left and right rear wheels 15 provided on left andright sides of a rear section thereof. The left and right front wheels14 are steered via a steering wheel 16 provided on a front section ofthe machine frame 13, and the left and right rear wheels 15 are drivenvia the power source 12.

As shown in FIGS. 2 to 5, the lawn mower 10 includes a housing 20, agrass clippings delivery passage (cut grass delivery passage) 22, leftand right cutting blades 31L and 31R, left and right auxiliary fans 40Land 40R, a grass clippings receptacle (cut grass receptacle) 51, and achute 52.

The housing 20 is disposed centrally on the underside of the machineframe 13. As shown in FIGS. 3 to 5, the housing 20 is formed generallyin a laterally-oriented “8” shape as viewed in top plan foraccommodating therein the left and right cutting blades 31L and 31R, andis open downwardly at its lower side.

Further, the housing 20 is formed in left-right symmetry respect to acenterline CL extending across the width of the housing 20 (i.e.,widthwise centerline CL), and it includes a left-half housing section21L and a right-half housing section 21R and a grass clippings deliverypassage 22 extending along the widthwise centerline CL. The left-halfhousing section 21L accommodates therein the left cutting blade 31L andthe left auxiliary fan 40L, while the right-half housing section 21Raccommodates therein the right cutting blade 31R and the right auxiliaryfan 40R.

Further, as viewed in top plan as in FIGS. 3, 5 and 6, the left-halfhousing section 21L has a scroll portion 23L gradually protruding upwardwhile winding spirally in a clockwise direction, and the right-halfhousing section 21R has a scroll portion 23R gradually protruding upwardwhile winding spirally in a counterclockwise direction. Namely, theleft-half housing section 21L and the right-half housing section 21R ofthe housing 20 are spiral cases or scroll cases which include the scrollportions 23L and 23R, respectively, for delivering grass cut by the leftand right cutting blades 31L and 31R (grass clippings) toward the grassclippings delivery passage (cut grass delivery passage) 22 whileswirling the grass clippings.

The grass clippings delivery passage (cut grass delivery passage) 22 isa passage for delivering the grass, cut by the left and right cuttingblades 31L and 31R, from a portion on the widthwise center CL (widthwiseportion of the housing 20) to the grass clippings receptacle 51 via thechute 52 by use of grass clippings delivering air (cut grass deliveringair), and it is formed in a generally rectangular sectional shape. Morespecifically, an entrance 22 a of the grass clippings delivery passage22 is open, along the widthwise centerline CL, from a front portion 20 cto a rear portion 20 d of the inner peripheral surface 20 e of thehousing 20. Further, the grass clippings delivery passage 22 extendsupwardly and rearwardly from the upper spirally-winding ends of the leftand right scroll portions 23L and 23R and has, at its rear end, an exit22 b (discharge outlet 22 b) connected to the chute 52.

The grass clippings receptacle 51 is provided on a rear section of themachine frame 13 behind the housing 20. The chute 52 connects from theexit 22 b at the rear end of the grass clippings delivery passage 22 tothe grass clippings receptacle 51. The chute 52 may be dispensed with asdesired, in which case the exit 22 b of the grass clippings deliverypassage 22 may be connected directly to the grass clippings receptacle51.

Further, as shown in FIGS. 5 and 6, the left and right cutting blades31L and 31R are accommodated within the housing 20 and rotatable ingenerally the same plane. More specifically, the housing 20 rotatablysupports, via bearings 33L and 33R, a pair of left and right driveshafts 32L and 32R disposed vertically along respective verticalcenterlines HL and HR of the left- and right-half housing sections 21Land 21R. Power of the drive source 13 (FIG. 1) is transmitted to theleft and right drive shafts 32L and 32R via a transmission member, suchas a belt. Within the housing 20, the two drive shafts 32L and 32R havethe left and right cutting blades 31L and 31R mounted separately ontheir respective distal end portions.

Further, the left and right cutting blades 31L and 31R are disposed witha 90° phase difference from each other. The left cutting blade 31Lrotates in a counterclockwise direction (i.e., direction of arrow Ru) ofFIG. 6 while the right cutting blade 31R rotates in a clockwisedirection (i.e., direction of arrow Rc) of FIG. 6, as viewed in bottomplan.

The left cutting blade 31L, which is an elongated blade formed inleft-right symmetry with respect to the left drive shaft 32L, has bladesections 31 a at its front edges in the rotational direction Ru and airlift sections 31 b at its rear edges in the rotational direction Ru. Bythe left cutting blade 31L rotating in the rotational direction Ru, theblade sections 31 a can cut grass, and the air lift sections 31 b cangenerate a flow of swirling air, i.e. swirling air flow Ws (or grassclippings delivering air Ws), in the left scroll portion 23L.

Similarly to the left cutting blade 31L, the right cutting flow 31R hasblade sections 31 a and air lift sections 31 b, and the air liftsections 31 b of the right cutting flow 31R can generate a flow ofswirling air, i.e. swirling air flow Ws (grass clippings delivering airWs), in the right scroll portion 23R.

The left and right auxiliary fans 40L and 40R are provided to increasethe amount of the grass clippings delivering air Ws generated by theleft and right cutting blades 31L and 31R and are disposed immediatelyover corresponding ones of the left and right cutting blades 31L and 31Rwithin the housing 20.

More specifically, the left auxiliary fan 40L is disposed immediatelyover the left cutting blade 31L within the left-half housing section 21Land includes a fan rotor 41. The fan rotor 41 includes a multiplicity ofblades and is mounted on the left drive shaft 32L. By rotating in thedirection of arrow Ru, the left auxiliary fan 40L absorbs external airthrough an air intake port 42 of the left-half housing section 21L andemits auxiliary grass clippings delivering air Wa.

The right auxiliary fan 40R, which is constructed similarly to the leftauxiliary fan 40L, is disposed immediately over the right cutting blade31RL within the right-half housing section 21R and includes a fan rotor41. By rotating in the direction of arrow Rc, the right auxiliary fan40R absorbs external air through an air intake port 42 of the right-halfhousing section 21R and emits auxiliary grass clippings delivering airWa.

Further, as shown in FIGS. 4 and 6, the housing 20 includes a deliveringair guide section 24 disposed in the front portion 20 c of the innerperipheral surface 20 b and along the widthwise centerline CL. Thedelivering air guide section 24 is formed in a generally V shapetapering from a front portion 20 b of the inner surface 20 a of thehousing 20 toward the entrance 22 a of the glass clippings deliverypassage 22 as viewed in top plan, so as to direct auxiliary grassclippings delivering air Wa, emitted from the left and right auxiliaryfans 40L and 40R, to the entrance 22 a of the grass clippings deliverypassage 22.

Grass clippings can be delivered to the grass clippings receptacle 51 bycomposite grass clippings delivering air Wt comprising main grassclippings delivering air Ws generated by rotation of the left and rightcutting blades 31L and 31R and auxiliary grass clippings delivering airWa generated by the left and right auxiliary fans 40L and 40R. Note thatthe left and right auxiliary fans 40L and 40R may be dispensed with asdesired. Thus, the term “grass clippings delivering air Wt” maysometimes refer to only the main grass clippings delivering air Ws.

Further, as shown in FIG. 4, the grass clippings delivery passage 22includes a bottom plate 22 c having a flat surface slanting obliquelyrearwardly and upwardly from a rear end portion of the housing 20. Thefront end of the bottom plate 22 c is located in the entrance 22 a ofthe grass clippings delivery passage 22. A scroll guide 60 and a shuttermechanism 80 are provided in the entrance 22 a of the grass clippingsdelivery passage 22.

Further, as shown in FIGS. 3 and 4, the scroll guide 60 is a member fordirecting both grass cut by the left and right cutting blades 31L and31R (grass clippings) and grass clippings delivering air to the grassclippings delivery passage 22 while swirling the grass clippings and thedelivering air within the housing 20. The scroll guide 60 is disposedalong the widthwise centerline CL of the housing and in left-rightsymmetry with respect to the widthwise centerline CL. The scroll guide60 is an integrally molded component that includes a base section 61located in the entrance 22 a of the grass clippings delivery passage 22and a guide body 71 extending forward from the base section 61 in aforward tapered shape.

Further, as shown in FIGS. 4, 7 and 8, the base section 61 of the scrollguide 60 has a flat bottom surface 62 superposed on the bottom plate 22c of the grass clippings delivery passage 22. A nut 63 is embedded inthe bottom surface 62 of the base section 61. The base section 61 isfastened at the bottom surface 62 to the bottom plate 22 c of the grassclippings delivery passage 22 by means of the nut 63 and a bolt 64.Thus, the scroll guide 60 is detachably attached to the bottom plate 22c of the grass clippings delivery passage 22.

The guide body 71 has an upper surface 72 slanting generally along theslant of the entrance 22 a of the grass clippings delivery passage 22.An inclination angle of the upper surface 72 relative to the lowersurface 20 a of the housing 20 is set such that the grass clippingsdelivering air can be smoothly introduced from the housing 20 to thegrass clippings delivery passage 22. For example, the inclination angleof the upper surface 72 is set such that the upper surface 72 extendssubstantially parallel to a top plate 22 d of the grass clippingsdelivery passage 22 slanting rearwardly and upwardly. Further, as shownin FIGS. 3 and 6, left and right side surfaces 73L and 73R are formed ina curved tapered shape generally along the inner surfaces of theleft-half housing section 21L and right-half housing section 21R.

The following describe in detail, with reference to FIGS. 4, 7, 9 and10, the scroll guide 61. An overall shape of the scroll guide 60 asviewed in top plan is a substantial isosceles triangle extending intothe housing 20 while tapering forward from the base section 61 (i.e.,from the base section 61 toward the front of the lawn mower 10).Further, an overall shape of the scroll guide 60 as viewed laterally inside elevation is a substantial triangle tapering forward from the basesection 61. Namely, the guide body 71 is formed in a substantialisosceles triangle as viewed in top plan and in a substantial triangleas viewed laterally in side elevation.

The left and right side surfaces 73L and 73R of the scroll guide 60,i.e. the left and right side surfaces 73L and 73R of the guide body 71,respectively comprise left and right substantial vertically-middleportions 74, i.e. left and right substantial middle height portions 74,and left and right lower slanting surfaces 75 and left and right upperslanting surfaces 76 formed as different slants below and above thesubstantial middle height portions 74. The “substantial middle heightportions 74” are height portions near the distal end 77 of the guidebody 71.

The left and right lower slanting surfaces 75 and the left and rightupper slanting surfaces 76 are each shaped to gradually increase in areain a direction from the distal end 77 of the scroll guide 60, i.e. thedistal end 77 of the guide body 71, toward the base section 61. Thescroll guide 60 is constructed as follows.

Namely, with the scroll guide 60 attached to the grass clippingsdelivery passage 22, the left and right lower slanting surfaces 75extend generally normally to the lower surface 20 a (FIG. 4) and havecurved surface portions arcuately recessed from the distal end 77 of thescroll guide 60 toward the base section 61.

Further, the left and right upper slanting surfaces 76 slant upwardlyfrom the distal end 77 of the scroll guide 60 toward the base section61. More specifically, the left and right upper slanting surfaces 76have curved surface portions arcuately recessed toward the base section61 while slanting upward from the distal end 77 of the scroll guide 60toward the base section 61.

The above-mentioned curved surface portions of the slanting surfaces 75and 76 are each recessed toward the widthwise centerline CL in agenerally arcuate shape corresponding to a rotating trajectory of acorresponding one of the left and right cutting blades 31L and 31R.Thus, in the mulching mode, it is possible to reduce a quantity of grassclippings, swirling within the housing 20, falling downward (i.e.,fall-down quantity of grass clippings), and thereby enhance theso-called grass retaining characteristic or performance.

As apparent from the foregoing, the scroll guide 60 projects forwardfrom the base section 61 in a substantial isosceles triangle as viewedin top plan and in a substantial triangle as viewed laterally in sideelevation. Therefore, when the lawn mower 10 is in the mulching mode, itis possible to prevent grass clippings, swirling within the housing 20,from falling down onto undesired portions.

Namely, in the mulching mode, the left and right lower slanting surfaces75 (i.e., lower slanting surfaces 75 of the left and right side surfaces73L and 73R) extend generally normally to the lower surface 20 a of thehousing 20 in order to adjust the fall-down quantity of the grassclippings swirling within the housing 20. Thus, in the mulching mode,the grass clippings swirling within the housing 20 can be caused tosmoothly swirl by means of the left and right side surfaces 73L and 73Ras well.

The left and right upper slanting surfaces 76 (i.e., upper slantingsurfaces 76 of the left and right side surfaces 73L and 73R), on theother hand, slant upward from the distal end 77 of the scroll guide 60toward the base section 61. Namely, the left and right upper slantingsurfaces 76 are twisted surfaces relative to the upper ends of the leftand right lower slanting surfaces 75. More specifically, the left andright upper slanting surfaces 76 are formed as twisted surfaces in orderto achieve both (1) enhancement of a grass delivery efficiency withwhich to discharge grass clippings from the housing 20 to the grassclippings delivery passage 22 in the bagging mode and (2) enhancement ofthe so-called grass retaining characteristic with which to adjust thefall-down quantity of the grass clippings swirling within the housing 20in the mulching mode.

In the aforementioned manner, the instant embodiment of the riding lawnmower 10 can achieve an enhanced grass delivery efficiency in thebagging mode and an enhanced grass retaining characteristic in themulching mode.

Of the base section 61 of the scroll guide 60, surfaces 65 facingradially inward of the housing 20, i.e. inwardly facing surfaces 65, areshaped to extend along the circular inner peripheral surface 20 e (FIG.10) of the housing 20. The inwardly facing surfaces 65 are formedcontinuously or integrally with proximal end portions of the left andright side surfaces 73L and 73R, so that grass clippings are allowed toswirl even more smoothly within the housing 20.

Further, of the scroll guide 60, the lower surfaces 78 (inner bottomsurfaces 78) located within the housing 20, more specifically at leastrear half portions 78 r of the lower surfaces 78 of the guide body 71,slant toward the base section 61. More specifically, the lower surfaces78 of the guide body 71 each include the rear half portion 78 r adjacentto the base section 61 and a front half portion 78 f located forward ofthe rear half portion 78 r. The front half portion 78 f extendssubstantially parallel to the lower surface 20 a of the housing 20 andlocated higher than the lower end 66 of the base section 61. The rearhalf portion 78 r curvingly slants rearwardly and downwardly from therear end of the front half portion 78 f to the lower end 66 of the basesection 61.

Because at least the rear half portions 78 r of the lower surfaces 78 ofthe guide body 71 slant downward toward the lower end 66 of the basesection 61, a swirling current fo (air current fo) within the housing 20is insusceptible to swirling resistance. Thus, grass clippings swirlingwithin the housing 20 can smoothly swirl without meeting swirlingresistance from the lower surface 78 of the scroll guide 60.

Further, as shown in FIGS. 4, 5 and 11, the distal end 31 c of each ofthe left and right cutting blades 31L and 31R (i.e., upper end 31 c ofeach of the air lift sections 31 b) is located higher by a height Hithan the distal end 77 of the scroll guide 60. Thus, grass clippingsswirling within the housing 20 is less likely to be subjected toresistance by the distal end 77 of the scroll guide 60, so that grassretaining performance or characteristic can be enhanced.

Further, in this case, turbulence is less likely to occur in a swirlingflow Fo as compared to a case where no height difference is providedbetween the distal end 31 c of the left and right cutting blades 31L and31R and the distal end 77 of the scroll guide 60. Besides, a rising aircurrent is generated by the air lift sections 31 b within the housing 20as the left and right cutting blades 31L and 31R rotate. Namely,negative pressure is generated over the left and right cutting blades31L and 31R, so that grass gr (FIG. 11) growing on the ground surfacebecomes easier to stand up by virtue of the negative pressure. Thus, thegrass gr can be cut or clipped with an increased reliability, leavingfewer grass gr undesirably uncut. As a result, enhanced grass cuttingperformance can be achieved.

The following describe, with reference to FIGS. 4, 7, 12 and 13, theshutter mechanism 80 employed in the instant embodiment. The shuttermechanism 80 is an opening/closing mechanism which is detachably mountedon a lower portion of the grass clippings delivery passage 22, and theshutter mechanism 80 is capable of opening and closing the grassclippings delivery passage 22. More specifically, the shutter mechanism80 is located immediately behind or rearward of the scroll guide 60,i.e. adjacent to the rear end of the scroll guide 60. The shuttermechanism 80 is constructed as a single unit that includes a base 81,pivot shaft 82, a shutter plate 83 and an operating force transmissionsection 84 as shown in FIG. 12.

The base 81 is a member mounted on a lower portion of the grassclippings delivery passage 22 and comprises left and right base halves91L and 91R separable from each other in a width direction of the base81. In a front view of the shutter mechanism 80, the left and right basehalves 91L and 91R are each of a substantially L shape, and thesubstantially L shapes of the right base halves 91L and 91R arehorizontally opposed to each other. Each of the left and right basehalves 91L or 91R is a member formed by bending a steel plate and has ahorizontal plate portion 92 elongated in the width direction of the base81, a flange portion 93 extending downward from the inner end, in thewidth direction, of the horizontal plate portion 92 and opposed to theflange portion 93 of the other base halve, and a vertical plate portion94 extending upward from the outer end, in the width direction, of thehorizontal plate portion 92 and opposed to the vertical plate portion 94of the other base halve 91R or 91L. The base 81 is assembled together bythe flange portions 93 of the left and right base halves 91L and 91Rbeing superposed on each other and fastened together by means of a bolt95.

Preferably, the pivot shaft 82 comprises a pair of horizontal shaftmembers 82 disposed on a lower portion of the grass clippings deliverypassage 22 and pivotably supported at its opposite end portions by thevertical plates 94 of the left and right base halves 91L and 91R. Thepivot shaft members 82 are provided on opposite lower end portions ofthe shutter plate 83.

The shutter plate 83 is a flat plate-shaped member pivotable about thepivot shaft 82 for opening or closing the grass clippings deliverypassage 22. Namely, the shutter plate 83 is pivotable between a fullyclosed position P1 for closing the grass clippings delivery passage 22to execute the mulching mode and a fully opened position P2 where it islaid down toward the discharge side of the grass clippings deliverypassage 22 to execute the bagging mode. The shutter plate 83 is operablebetween the fully closed position P1 and the fully opened position P2via an operation section 110 (FIG. 1) located remote from the shuttermechanism 80.

The operating force transmission section 84 is a mechanism fortransmitting opening/closing operation force, given via the operationsection 110, to the shutter plate 83. The operating force transmissionsection 84 includes: a pivot arm 101 mounted on one of the pivot shaftmembers 82 for limited relative pivoting movement; a return spring 102normally urging the shutter plate 83 toward the opened position; and anengagement section 103 that hooks one end of the return spring 102.

The swing arm 101 is a plate-shaped bar that, when the shutter mechanism80 is assembled, is mounted on the one pivot shaft 82 to extend inopposite directions from the pivot shaft 82. The other end of the returnspring 102 is hooked by one end portion of the swing arm 101. Further,an inner wire 104 a of a wire cable 104 is connected at one end portionto another end portion of the pivot arm 101, and an outer tube 104 bcovering the inner tube 104 a is fixed at one end portion to a fasteningportion 103 a of the engagement section 103.

The return spring 102 is in the form of a tension spring. The engagementsection 103 is integrally provided on one of the left and right verticalplates 94, and the one vertical plate 94 has a stopper 105. The stopper105 is a member that defines the fully closed position P2 of the shutterplate 83, and, in the fully closed position P2 of the shutter plate 83,the other end portion of the swing arm 101 is abutted by the stopper105.

Further, as shown in FIG. 7, the pivot shaft 82 and the shutter plate 83are disposed with a space Sp from the bottom plate 22 c (bottom surface)of the grass clippings delivery passage 22. Namely, a height at whichthe pivot shaft 82 is supported by the base 81 is set in such a manneras to form the space Sp.

Further, when the shutter plate 83 is in the fully opened position, P2as shown in FIGS. 4 and 7, the shutter plate 83 extends generally inflush with the upper surface 72 of the scroll guide 60, which allows thegrass clippings delivering air to flow smoothly. A downwardly-recessedstepped section 68 for accommodating therein the pivot shaft 82 of theshutter mechanism 80 is formed at the rear end 67 of the base section61. More specifically, the stepped section 68 is formed by recessing anupper corner portion of the rear end 67 in a generally semi-circularshape as viewed laterally in side elevation.

Further, as shown in FIG. 8, the unitized shutter mechanism 80 isinserted onto the bottom plate 22 c of the grass clippings deliverypassage 22, for example, from behind the passage 22, or superposed onthe bottom plate 22 c from below or above the bottom plate 22 c. Then,the unitized shutter mechanism 80 can be assembled or attached to thegrass clippings delivery passage 22 by the base 81 being fastened to thebottom plate 22 c by means of a bolt 85. Then, the unitized shuttermechanism 80 can be disassembled or detached from the grass clippingsdelivery passage 22 by the base 81 being detached from the bottom plate22 c. Therefore, a cleaning operation of the shutter mechanism 80 can besimplified.

Further, as shown in FIG. 1, the operation section 110 for operating theshutter mechanism 80 is disposed near the seat 11 of the riding lawnmower 10. Namely, an operating lever 115 of the operation section 110 isdisposed at a position operable by a hand, e.g. left hand, of the humanoperator seated in the seat 11.

Further, as shown in FIGS. 14 and 15, the operation section 110includes: a bracket 111 fixed to the machine frame 13; a first shaft 112rotatably supported at opposite ends on the bracket 111; a pivot arm 113mounted on the first shaft 112; a second shaft 114 mounted at oppositeends on the pivot arm 113; the operating lever 115 pivotably supportedon the second shaft 114; and a return spring 116 for normally urging theoperating lever 115.

The first shaft 112 is rotatable in a front-rear direction of themachine frame 13, so that the pivot arm 113 is also rotatable in thefront-rear direction of the machine frame 13. The inner wire 104 a ofthe wire cable 104 is connected at its other end portion to one endportion of the pivot arm 113, and the other end portion of the outertube 104 b covering the inner tube 104 a is fastened to the fasteningportion 117 of the bracket 111.

The operating lever 115 is pivotable relative to the pivot arm 113 in adirection perpendicular to the first shaft 112, i.e. in a widthdirection (vertical direction in FIG. 14) of the machine frame 13. Theoperating lever 115 has its proximal end portion covered with a cover119 having a generally crank-shaped guide groove 118 as viewed in topplan. The return spring 116 is in the form of a torsion spring andnormally urges the operating lever 115 inward in the width direction ofthe machine frame 13.

Usually, the operating lever 115 is held in a generally upright orstand-up bagging position Ba as shown in FIG. 14. In this state, theshutter plate 83 shown in FIG. 4 is held in the fully opened position P2for fully opening the grass clippings delivery passage 22, so that thelawn mower 10 is allowed to operate in the bagging mode.

Then, as necessary, the operating lever 115 is shifted forward anddownward over to a mulching position Mu while being guided along thecrank-shaped guide groove 118. At that time, the pivot arm 113 pivotscounterclockwise in FIG. 14 to thereby pull the inner wire 104 a. Thus,the pivot arm 101 pivots counterclockwise in FIG. 12, so that theshutter plate 83 pivots counterclockwise in FIG. 12 to thereby stand up.In this manner, the shutter plate 83 stands up to the fully closedposition P1 as indicated by imaginary line in FIG. 4, to thereby fullyclose the grass clippings delivery passage 22. As a result, the lawnmower 10 can be switched from the bagging mode to the mulching mode.

Then, as necessary, the operating lever 115 shown in FIG. 14 is shiftedrearward and downward over to the bagging position Ba while being guidedagain along the crank-shaped guide groove 118. Thus, the lawn mower 10is switched to the bagging mode Ba, and the shutter plate 83 can beshifted back to the fully opened position P2 as indicated by solid linein FIG. 4. As a result, the lawn mower 10 can be switched from themulching mode back to the bagging mode.

The description about the shutter mechanism 80 constructed in theaforementioned manner can be summarized as follows. The shuttermechanism 80 employed in the instant embodiment is of a so-called fronthinge type where the pivot point (pivot shaft 82) of the shutter plate83 is disposed on a front portion of the shutter plate 83. Because theshutter mechanism 80 is of such a front hinge type, the hinge section(i.e., pivot shaft 82 and support portions for the pivot shaft members82) of the shutter mechanism 80 and other component parts around thehinge section are located near the entrance 22 a of the grass clippingsdelivery passage 22. Because the entrance 22 a is connected to thehousing 20, the grass clippings delivering air Wt (Ws) has a relativelygreat force in the neighborhood of the entrance 22 a, so that grassclippings are less likely to fall on and around the hinge section. Evenin case grass clippings have fallen and accumulated on and around thehinge section, they can be easily blown away by the strong grassclippings delivering air Wt (Ws). Thus, it is possible to effectivelyprevent unwanted jamming of grass clippings in the shutter mechanism 80,particularly in the hinge section, as a result of which the instantembodiment can minimize the frequency of maintenance/inspection andcleaning operations to be performed on the shutter mechanism 80.

Further, because the shutter mechanism 80 is a unitized mechanism(constructed as a single unit), it can be detachably attached togetheras the unit to the grass clippings delivery passage 22. Thus, at thetime of maintenance/inspection or cleaning operations, the shuttermechanism 80 can be easily and simply detached and attached from and tothe grass clippings delivery passage 22. As a result,maintenance/inspection and cleaning operations can be performed withease on the shutter mechanism 80 and the interior of the grass clippingsdelivery passage 22.

Furthermore, the pivot shaft 82 and the shutter plate 83 are disposedwith the space Sp from the bottom plate 22 c (bottom surface 22 c) ofthe grass clippings delivery passage 22. Generally, as the cuttingblades 31L and 31R stop rotating, the grass clippings delivering air Wt(Ws) stops being generated, and thus, grass clippings would fall andaccumulate on the bottom surface 22 c of the grass clippings deliverypassage 22 and on and around the hinge section. However, by theprovision of the above-mentioned space Sp, grass clippings are lesslikely to accumulate on the pivot shaft 82 and the shutter plate 83 andjam in the shutter mechanism 80.

Furthermore, the downwardly-recessed stepped section 68 foraccommodating therein the pivot shaft 82 of the shutter mechanism 80 isformed in the rear end 67 of the scroll guide 60 provided in theentrance 22 a of the grass clippings delivery passage 22. Thus, when theshutter plate 83 is in the fully opened position P2 where it is laiddown toward the discharge side (output side) of the grass clippingsdelivery passage 22, the hinge section does not project into the grassclippings delivery passage 22. Namely, the shutter mechanism 80 has nostepped section in and around the hinge section. Thus, even when grasscuttings have fallen on the bottom surface 22 c of the grass clippingsdelivery passage 22, they do not accumulate on the bottom surface 22 cbecause they can be easily blown away by the grass clippings deliveringair Wt(Ws). Thus, it is possible to effectively prevent jamming of grassclippings in the hinge section, as a result of which the instantembodiment can even further minimize the frequency ofmaintenance/inspection and cleaning operations. Besides, because theshutter mechanism 80 has no stepped section in and around the hingesection, any particular construction is not required to eliminate astepped section from the hinge section.

Now, a description will be given about behavior of the scroll guide 60in the case where the lawn mower 10 is used selectively in any desiredone of the bagging mode and mulching mode as necessary.

FIG. 16( a) shows flows of grass clippings delivering air and grassclippings in the case where the lawn mower 10 is used in the baggingmode, and FIG. 16( b) shows flows of grass clippings delivering air andgrass clippings as viewed from the entrance 22 a of the grass clippingsdelivery passage 22.

As shown in FIGS. 6, 16(a) and 16(b), the grass clippings deliverypassage 22 is kept opened while the lawn mower 10 is in the baggingmode.

Grass cut by the left and right cutting blades 31L and 31R (i.e., grassclippings) are directed to the upper surface 72 of the scroll guide 60and the shutter plate 83 while swirling within the housing 20 and thenflow along the grass clippings delivery passage 22. Thus, the grassclippings swirling within the housing 20 can be efficiently delivered tothe grass clippings delivery passage 22.

FIG. 17( a) shows flows of grass clippings delivering air and grassclippings in the case where the lawn mower 10 is used in the mulchingmode, and FIG. 17( b) shows flows of grass clippings delivering air andgrass clippings as viewed from the entrance 22 a of the grass clippingsdelivery passage 22.

As shown in FIGS. 6, 17(a) and 17(b), the grass clippings deliverypassage 22 is kept closed while the lawn mower 10 is in the mulchingmode. Grass clippings grc can be discharged downward of the housing 20after being sufficiently chopped into finer pieces while swirling withinthe housing 20.

The description about the scroll guide 60 constructed in theaforementioned manner can be summarized as follows. The left and rightside surfaces 73L and 73R of the scroll guide 60 each comprise thesubstantial middle height portion 74, and the lower slanting surface 75and the upper slanting surfaces 76 formed as different slants below andabove the substantial middle height portion 74. By setting appropriateslant angles of the aforementioned individual slanting surfaces, it ispossible to optimize flows of the grass clippings delivering air Wt (Ws)and grass clippings irrespective of whether the lawn mower 10 is in themulching mode or in the bagging mode. Thus, grass clippings can beefficiently discharged downward of the housing 20 in mulching mode,while grass clippings can be efficiently collected in the grassclippings receptacle 51 in the bagging mode. Besides, when the lawnmower 10 is switched from the bagging mode to the mulching mode or fromthe mulching mode to the bagging mode, there is no need to replace apredetermined component part specific to the previous or switched-frommode with a component part specific to the new or switched-to mode inorder to optimize the flows of flows of the grass clippings deliveringair Wt (Ws) and grass clippings.

In the mulching mode, the instant embodiment can prevent grassclippings, swirling within the housing 20, from undesirably falling downin the neighborhood of the entrance 22 a of the grass clippings deliverypassage 22 and thus can effectively retain the grass within the housing20 (i.e., achieve an enhanced grass retaining characteristic).Therefore, the instant embodiment can discharge the grass clippingsdownward of the housing 20 after sufficiently chopping the grassclippings to finer pieces. Further, in the bagging mode, the instantembodiment can efficiently deliver grass clippings, swirling within thehousing 20, to the grass clippings delivery passage 22.

Finally, the basic principles of the present invention are well suitedparticularly for application to riding lawn mowers each of whichincludes left and right cutting blades and is capable of operating bothin a bagging mode and in a mulching mode.

What is claimed is:
 1. A riding lawn mower comprising: a housing openingdownward; a cut grass receptacle disposed rearward of the housing; leftand right cutting blades accommodated in the housing and rotatable ingenerally a same plane in such a manner as to not only cut grass butalso generate cut grass delivering air; a cut grass delivery passage fordelivering grass, cut by the left and right cutting blades, from awidthwise center portion of the housing to the cut grass receptacle byuse of the cut grass delivering air; a mechanism for switching the lawnmower between a bagging mode in which grass cut by the cutting blades isdelivered from the housing to the cut grass receptacle and a mulchingmode in which grass cut by the cutting blades is discharged downward ofthe housing; and a scroll guide provided in an entrance of the cut grassdelivery passage for directing the cut grass to the cut grass deliverypassage and the delivering air while swirling the cut grass and thedelivering air within the housing, wherein an overall shape of thescroll guide is, as viewed in top plan, a substantial isosceles triangleextending into the housing while tapering forward from a base section ofthe scroll guide located in the entrance, and, as viewed in sideelevation, a substantial triangle tapering forward from the basesection, and left and right side surfaces of the scroll guide eachcomprise a lower slanting surface and an upper slanting surface formedas different slants below and above a substantial middle height portionthereof, each of the lower slanting surface and the upper slantingsurface being shaped to gradually increase in area in a direction from adistal end of the scroll guide toward the base section.
 2. The ridinglawn mower according to claim 1, wherein the lower slanting surfaces ofthe left and right side surfaces of the scroll guide extend generallynormally to a lower surface of the housing, and the upper slantingsurfaces of the left and right side surfaces of the scroll guide slantupward from the distal end of the scroll guide toward the base section.3. The riding lawn mower according to claim 1, wherein a distal end ofeach of the left and right cutting blades is located at a higherposition than the distal end of the scroll guide.
 4. The riding lawnmower according to claim 1, wherein, of the base section of the scrollguide, surfaces facing radially inward of the housing are shaped toextend along an inner peripheral surface of the housing.
 5. The ridinglawn mower according to claim 1, wherein at least a rear half portion ofa lower surface, located within the housing, of the scroll guide slantstoward the base section.